From the record
“The Mariscal Mine, also known as the Lindsey Mine and the Ellis Mine, was a source of cinnabar ore that was refined at the Texas site into mercury. The mine is located in what is now Big Bend National Park.”
Wikipedia article Mariscal Mine, CC BY-SA 4.0.
One of 14 National Register listings published here for Brewster County · listed in 1974 · category: District.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service